U.S. Pat. No. 4,997,096 discloses a child-resistant closure having inner and outer plastic shells. The outer plastic shell has a base wall, a peripheral skirt and a circumferential array of lugs on an underside of the base wall. The inner shell has a base wall, a peripheral skirt, at least one internal thread on the skirt, and a circumferential array of lugs on an outer surface of the base wall for opposed engagement by the internal lugs on the base wall of the outer shell. To remove the closure when it is threaded onto a container finish, the outer shell must be pushed axially against the inner shell and simultaneously rotated so that the lugs of the outer shell engage the lugs of the inner shell and rotate the inner shell with respect to the container finish. When the outer shell is rotated without applying an axial force to the outer shell, the lugs on the outer shell simply cam over the lugs on the inner shell and do not rotate the inner shell with respect to the container finish. Child-resistant closures of the type illustrated in this patent have been marketed for many years by applicants' assignee under the trademark ARGUS-LOC. See also GB 1529999. In some instances, child-resistant packaging is not required, and it is a general object of the present invention to provide a closure of the type disclosed in the above-noted U.S. patent that possesses a non-child-resistant mode of operation in which the closure can be readily removed from a container finish.
A closure in accordance with the present invention includes an outer plastic shell having a base wall, a peripheral skirt with a central axis, a circumferential array of lugs on an underside of the base wall, and a pair of axially spaced internal beads on the skirt spaced from the base wall. An inner plastic shell has a base wall, a peripheral skirt with a central axis, at least one internal thread on the skirt of the inner shell, a circumferential array of lugs on an outer surface of the base wall, and a circumferential bead on an outer surface of the skirt remote from the base wall. The inner shell is positionable within the outer shell in a non-child-resistant first position with the bead on the skirt of the inner shell captured between the beads on the skirt of the outer shell, such that the outer shell is rotatably coupled to the inner shell and the at least one internal thread on the skirt of the inner shell can be threaded onto and off of a container by simple rotation of the outer shell. The inner shell is positionable within the outer shell in a child-resistant second position with the bead on the inner shell skirt spaced from the beads on the outer skirt, such that rotation of the outer shell is imparted to the inner shell by forced engagement of the lugs on the base walls.
In the preferred embodiments of the invention, the internal bead on the outer shell skirt further from the base wall of the outer shell has a lesser internal diameter than the internal bead closer to the base wall of the outer shell, and cooperates with the external bead on the inner shell to retard removal of the inner shell from within the outer shell. The base wall of the outer shell preferably has an opening into which a dome on the inner shell extends in the child-resistant position of the inner shell with respect to the outer shell. This dome helps facilitate manual movement of the inner shell from the child-resistant to the non-child-resistant position, and helps prevent entry of debris through the opening of the outer shell in the child-resistant position.